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fix for MX25R1635F QSPI mode of operation #4460

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Merged
merged 2 commits into from
Mar 22, 2021
Merged

fix for MX25R1635F QSPI mode of operation #4460

merged 2 commits into from
Mar 22, 2021

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lyusupov
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When the MX25R1635F flash IC is connected to nRF52840 over quad-SPI bus - the CircuitPython does not boot.

Primary reason for that is incorrect 'quad_enable_bit_mask' definition used in current 'devices.h'
This is an excerpt from the datasheet:

image

For compatibility reasons with all the family of the MX25R1635F IC's and with all the modes of operation it is worth to lower SPI clock frequency down to 8 MHz:

image

This PR fixes the issue - it is confirmed that MX25R1635F is doing good in QSPI mode afterwards.

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Thank you! I don't have the hardware to verify, but I also noticed these changes bring things in line with the above MX25R6435F part.

The two devices still have a different start_up_time_us, not sure if important. If CircuitPython is loaded from a uf2 bootloader, as is customary on Adafruit boards, it does not matter.

@tannewt looks like you may need to pick up this change for nvm.toml.

@jepler jepler merged commit 2373e64 into adafruit:main Mar 22, 2021
@lyusupov
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@jepler Thank you for the review and merge actions!

800 us of 'start_up_time_us' is good enough. It is specified as a minimum value in the datasheet:

image

@lyusupov lyusupov deleted the MX25R1635F_QSPI_FIX branch March 22, 2021 14:16
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jepler commented Mar 22, 2021

Excellent, thank you for that info

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2 participants